Dissertation Research: Phylogeny of Aplacophora and Polyplacophora and Evolution of Molluscan Calcareous Hard Parts

论文研究：无壳纲、多壁纲的系统发育及软体动物钙质硬质部分的演化

• 批准号: 0073312
• 负责人: Andrew Knoll
• 金额: $ 1万
• 依托单位: Harvard University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-06-01 至 2002-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0073312&HistoricalAwards=false
• 关键词: Dissertation; Research; Phylogeny; Aplacophora; Polyplacophora

0073312Knoll and OkusuGraduate student Akiko Okusu, under the direction of Dr. Andrew Knoll, Harvard University, is studying the phylogenetic relationships and the evolution of calcareous hard parts of aplacophoran and polyplacophoran molluscs using integrated data from DNA sequences, morphology, and embryology. Aplacophorans are worm-like deep-sea molluscs that have no shells but are covered by spicules made of the calcium carbonate mineral aragonite. Polyplacophorans (chitons) are flat elongate molluscs with eight dorsal shell-plates imbricated within a spicule-embedded mantle girdle. It has been postulated that aplacophorans are closely related to polyplacophorans, that the two groups represent the most basal groups of molluscs (based on their relatively simple features), and that their aragonite spicules reflect a more "primitive" type of calcium carbonate deposition than that found in other molluscs. However, the evolutionary relationships of the Aplacophora and the Polyplacophora are unresolved. The lack of a well-supported phylogeny calls into question hypotheses of evolutionary changes in molluscan form and mineral deposition. Molecular sequence data from highly conserved nuclear coding genes, EF1-alpha and POL-II, will be used to construct a phylogenetic framework for 40 taxa including representative species from major molluscan classes and outgroup species from the Sipuncula and Annelida. Spicule development and morphology in these groups will be analyzed within the phylogenetic framework in order to assess homology and pattern of evolutionary change. The results will have a major impact on our understanding of the origin and evolution of molluscs.

0073312Knoll和Okusu研究生Akiko Okusu在哈佛大学Andrew Knoll博士的指导下，利用DNA序列、形态学和胚胎学的综合数据，研究了无足纲和多足纲软体动物的钙质硬部分的系统发育关系和进化。无壳类是一种蠕虫状的深海软体动物，没有贝壳，但被由碳酸钙矿物文石制成的针状物覆盖。多囊类是一种扁平的细长软体动物，有八个背部壳板，覆盖在一个嵌有针刺的地幔环带内。据推测，无足类与多足类关系密切，这两个类群代表了软体动物中最基本的类群(基于它们相对简单的特征)，它们的文石针状物反映了比在其他软体动物中发现的更原始的碳酸钙沉积类型。然而，拟盘亚目和多盘亚目的进化关系尚未解决。缺乏得到充分支持的系统发育，使软体动物形态和矿物沉积的进化变化假说受到质疑。来自高度保守的核编码基因EF1-α和POL-II的分子序列数据将被用来构建40个分类群的系统发育框架，其中包括主要软体动物纲的代表性物种和来自Sipuncula和环节动物纲的外群物种。这些类群的毛刺发育和形态将在系统发育框架内进行分析，以评估同源性和进化变化的模式。这一结果将对我们理解软体动物的起源和进化产生重大影响。